A conventional blood flow dynamic analyzing apparatus uses, for example, an X-ray CT apparatus to carry out dynamic imaging. During the imaging, an iodine-based contrast medium is injected into a patient. The blood flow dynamic analyzing apparatus thus provides information on a temporal variation in the concentration of the injected contrast medium. A time-concentration curve can be obtained from the temporal variation. Then, by analyzing the curve of the time-concentration curve, it is possible to obtain biological function information such as blood flow dynamics. Typical algorithms for analyzing the blood flow dynamics include a first moment method (gamma-fitting method), a maximum slope method, and a deconvolution method.
First, the first moment method (gamma-fitting method) uses a gamma function to approximate the time-concentration curve. Then, blood flow information is calculated from a peak value of the approximate curve and an area under the curve. Next, the maximum slope method calculates a blood flow by dividing the maximum value of slope of the time-concentration curve for each tissue by the maximum value of a rise in a CT value in an arterial input function.
However, the first moment method (gamma-fitting method) and the maximum slope method require that about 8 to 10 ml/sec of contrast medium be injected into the subject. Disadvantageously, this is a heavy burden on the physical strength of the subject into which the contrast medium is injected. Moreover, disadvantageously, the gamma fitting method enables qualitative evaluation but not quantitative evaluation.
Thus, efforts were made to develop a blood flow analyzing method which can reduce the contrast rate and which enables quantitative evaluation. As a result, the deconvolution method has been proposed (see the well-known document shown below). The deconvolution method subjects an arterial input function and a tissue output function to deconvolution to generate an impulse residue function. Then, blood flow information is calculated from a peak value or an area under the curve of the impulse residue function generated. The deconvolution method advantageously enables examinations at a low contrast rate of about 3 to 5 ml/sec. Accordingly, the deconvolution method requires a contrast medium injection speed that is only about half that of the first moment method (gamma-fitting method) or the maximum slope method.
(Well-known document: L. Ostergarrd etc.: High Resolution Measurement of Cerebral Blood Flow using Intravascular Tracer Bolus Passages: 1996; Magnetic Resonance in Medicine Vol. 36: P. 715-725)
However, the deconvolution method requires a plurality of integrations in the data conversion calculation that determines the impulse residue function from the arterial input function and tissue output function. Consequently, the deconvolution method requires a time for the calculation.
It is an object of the present invention to enable blood flow dynamic analysis to be carried out in a short time.